Understanding population connectivity across habitats is critical for population management and conservation. Thirty-one management units have been delimited for common bottlenose dolphin (Tursiops truncatus) populations in Gulf of Mexico bays, sounds, and estuaries (BSEs). However empirical data are lacking across many areas to corroborate these delineations or to evaluate the long-term consequences of fine-scale structure in the face of increasing anthropogenic pressures and global climate change. We addressed this data gap by estimating baseline genetic diversity and population structure of T. truncatus in the BSEs of the Florida Panhandle.
Skin samples from T. truncatus were collected in Pensacola Bay, Choctawhatchee Bay, and St. Andrew Bay between 2015 and 2016. A 353 base pair section of the mitochondrial DNA (mtDNA) control region was sequenced for each sample and individuals were genotyped at 19 microsatellite loci. Population assignment was conducted using the Bayesian clustering program STRUCTURE with microsatellite data (N = 168). Analysis of molecular variance (AMOVA) was used to estimate FST for pairwise comparisons using both datasets and ФST using mtDNA data (N = 157).
Results/Conclusions
Nine haplotypes were found across sites, two of which were only found in Choctawhatchee Bay. Haplotype (h) and nucleotide diversity (p) were similar between Pensacola (h = 0.839; p = 0.006) and Choctawhatchee Bays (h = 0.825; p = 0.007) but notably lower in St. Andrew Bay (h = 0.544; p = 0.003). Preliminary results show that St. Andrew Bay was assigned by STRUCTURE as a distinct population. Results from pairwise comparisons were congruent; St. Andrew Bay significantly differed from Pensacola and Choctawhatchee Bays across all markers tested (mtDNA: FST = 0.099-0.173, ФST = 0.062-0.063, p < 0.01 for all tests; microsatellites: FST = 0.020-0.028, p < 0.001 for all tests). Further analyses on microsatellite data are in progress to account for relatedness, unequal sample sizes, and to further explore hierarchical genetic structure.
With life history traits such as late maturity, low fecundity, and slow population growth, common bottlenose dolphins are vulnerable to resource depletion and Unusual Mortality Events. Our results will provide updated information for population assessments to resource managers and contribute to a growing body of literature necessary to better understand the drivers of fine-scale genetic population structure in T. truncatus.